• Title/Summary/Keyword: Impact Hammer

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An Enhancement of Transfer Function Synthesis by Improving the Leakage Error of FRF (FRF 누설오차 개선에 의한 전달함수 합성법의 향상)

  • Ahn, Se-Jin;Jeong, Weui-Bong;Kim, Seung-Yup
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.517-522
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    • 2002
  • The frequency response function(FRF) of each substructure is used for the transfer function synthesis method(TFS). The dynamic characteristics of the full system are obtained by synthesizing FRFs of each substructure. The validation of TFS depends on accuracy for FRF of each substructure. Impact hammer testing is widely used to obtain the modal characteristics of structures. However, the FRF obtained from impact hammer testing contains several errors, such as finite record length error and leakage error of which characteristic depends on data acquisition time which we call record length. In this paper, a method to remove these errors is proposed so as to enhance results of TFS. Numerical examples show that the FRF of full structure can be predicted exactly by the method proposed in this paper.

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Identification of Rigid Body Properties of the Mounted Structure with Improved Mass-Lines from Impact Hammer Tests (탄성지지된 구조물의 충격 햄머 실험에서 질량선의 개선을 통한 향상된 강체 특성 규명법)

  • Ahn, Se-Jin;Jeong, Weui-Bong;Hwang, Dae-Sun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.317-322
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    • 2002
  • There are many researches to identify the rigid body properties from the mass-line obtained by impact hammer testing. The correct rigid body properties of the structure may be estimated if the mass-line of the structure could be obtained exactly. When the structure is mounted by elastic materials, the mass-line cannot be read correctly from the impulse response spectrum. The reason is due to the effects of rigid body modes of mounted structure. In this paper, the effects of rigid body modes of mounted structure to the mass-line are discussed and the method to remove these effects is also presented.

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Modeling and Validation of RK4 Multi Axis Rotor system (RK4 다축 회전체 시스템의 동역학모델링 및 검증)

  • Kwonn, Ki Beom;Han, Jeong Sam;Jeon, ByungChul;Jung, Joonha;Youn, Byeng D.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.04a
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    • pp.233-237
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    • 2014
  • In this paper, the finite element modeling of the RK4 rotor kit system (RK4) and then frequency analysis and transient analysis, and was compared with the actual experimental results. RK4 manufactured by General Electric for the purpose of education and research. It is composed of two shaft, Two shaft is connected using a flexible coupling, one disk is mounted. The analytical model is modeled by using the ANSYS finite element analysis program commercially available. Based on impact hammer test results, material properties and the stiffness of the bearing and coupling was tuned. Considering the operating conditions and the vibration response of the analytical model were compared with experimental results.

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The Identification of Rigid Body Properties with Improved Mass-Lines from Impact Hammer Tests of The Mounted Structure (탄성지지된 구조물의 충격 햄머 실험에서 질량선의 개선을 통한 향상된 강체 특성 규명법)

  • Ahn, Se-Jin;Jeong, Weui-Bong;Hwang, Dae-Sun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.336.2-336
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    • 2002
  • There are many researches to identify the rigid body properties from the mass-line obtained by impact hammer testing. The correct rigid body properties of the structure may be estimated if the mass-line of the structure could be obtained exactly. When the structure is mounted by elastic materials, the mass-line cannot be read correctly from the impulse response spectrum. The reason is due to the effects of rigid body modes of mounted structure. (omitted)

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A Suggestion of Method to Remove Bias Error of the FRF Obtained by FFT Analyzer - Application of TFS - (계측기에서 얻어진 주파수 응답 함수의 오차 제거 방안 - 전달함수 합성법에의 응용 -)

  • 김승엽;정의봉;서영수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.408-413
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    • 2003
  • The frequency response function(FRF) of each substructure is used for the transfer function synthesis method(TFS). The dynamic characteristics of the full system are obtained by synthesizing FRFs of each substructure. The validation of TFS depends on accuracy for FRF of each substructure. Impact hammer testing Is widely used to obtain the modal characteristics of structures However. the FRF obtained from impact hammer testing contains bias errors, such as finite record length error and leakage error of which characteristic depends on data acquisition time which we call record length. In this paper, a method to remove hose errors is proposed so as to enhance results of TFS. Numerical and experimental examples show that the FRF of full structure can be predicted nearly exactly by the method proposed in this paper.

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Experimental Analysis of Vibration of Annular Plate in Contact with Water (원환판의 접수진동 해석에 대한 실험적 연구)

  • 한상보;곽문규;송장규;김윤환
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.431-437
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    • 1996
  • The natural frequencies of annular plates in contact with water were theoretically derived and its validity was checked by experiments. The experimental frequency response functions of the annular plates were obtained using the impact hammer method. Comparison of the FRF obtained using the impact hammer and the fRF using shaker attached showed that the former was better than the latter due to the mass effect and additional constraint from the instrumentation. It was found that the experimentally extracted natural frequencies of annular plates in contact with water were in good agreement with those theoretical values.

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Performance evaluation of the lightweight concrete tapered piles under hammer impacts

  • Tavasoli, Omid;Ghazavi, Mahmoud
    • Geomechanics and Engineering
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    • v.18 no.6
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    • pp.615-626
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    • 2019
  • Lightweight concrete (LWC) provides an attractive alternative to conventional piles by improving the durability of deep foundations. In this paper, the drivability of cylindrical and tapered piles made of lightweight and common concrete (CC) under hammer impacts was investigated by performing field tests and numerical analysis. The different concrete mixtures were considered to compare the mechanical properties of light aggregate which replaced instead of the natural aggregate. Driving tests were also conducted on different piles to determine how the pile material and geometric configurations affect driving performance. The results indicated that the tapering shape has an appropriate effect on the drivability of piles and although lower driving stresses are induced in the LWC tapered pile, their final penetration rate was more than that of CC cylindrical pile under hammer impact. Also by analyzing wave propagation in the different rods, it was concluded that the LWC piles with greater velocity than others had better performance in pile driving phenomena. Furthermore, LWC piles can be driven more easily into the ground than cylindrical concrete piles sometimes up to 50% lower hammer impacts and results in important energy saving.

A Study on Thermal Flow Analysis in Grinding Disc Assembly for Disintegration of Secondary Battery Materials (이차전지 원료 해쇄용 그라인딩 디스크 어셈블리 내 열 유동 해석에 관한 연구)

  • Dong-Min Yun;Yong-Han Jeon
    • Design & Manufacturing
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    • v.16 no.4
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    • pp.34-39
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    • 2022
  • Sustained economic development around the world is accelerating resource depletion. Research and development of secondary batteries that can replace them is also being actively conducted. Secondary batteries are emerging as a key technology for carbon neutrality. The core of an electric vehicle is the battery (secondary battery). Therefore, in this study, the temperature change by the heat source of the hammer and the rotational speed (rpm) of the abrasive disc of the Classifier Separator Mill (CSM) was repeatedly calculated and analyzed using the heat flow simulation STAR-CCM+. As the rotational speed (rpm) of the abrasive disk increases, the convergence condition of the iteration increases. Under the condition that the inlet speed of the Classifier Separator Mill (CSM) and the heat source value of the disc hammer are the same, the disc rotation speed (rpm) and the hammer temperature are inversely proportional. As the rotational speed (rpm) of the disc increases, the hammer temperature decreases. However, since the wear rate of the secondary battery material increases due to the strong impact of the crushing rotational force, it is determined that an appropriate rpm setting is necessary. In CSM (Classifier Separator Mill), it is judged that the flow rate difference is not significantly different in the direction of the pressure outlet (Outlet 1) right above the classifier wheel with the fastest flow rate. Because the disc and hammer attachment technology is adhesive, the attachment point may deform when the temperature of the hammer rises. Therefore, it is considered necessary to develop high-performance adhesives and other adhesive technologies.

Investigation of Error Factors from an Impact Hammer Test for Developing a Statistic Based Technique for Model Updating (통계 기반 모델 개선을 위한 임팩트 해머 실험의 오차 요인 분석)

  • Lee, Su;Lee, Jin Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.2
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    • pp.185-198
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    • 2016
  • In this work, experimental errors from an impact hammer test were investigated to develop a statistic-based technique for updating a finite element model. Digital signal processing was analyzed by using theoretical models and experiments when errors occurred during the experimental procedure. First, the duration time and peak level of the excitation signal, the stiffness and position of elastic springs connecting the specimen as well as the support, position and mass of the accelerometer were considered as error factors during the experiment. Then the picket fence effect, leakage, and exponential window function were considered as candidate error factors during the digital signal processing. Finally, methods to reduce errors are suggested.

Laboratory Tests for the Applicability of Various Testing Devices for Measuring Degree of Compaction (여러가지 다짐 평가장비의 적용성을 위한 실내시험)

  • Yoo, Wan-Kyu;Lim, Nam-Gyu;Kim, Byoung-Il;Kim, Ju-Hyong
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.1178-1187
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    • 2008
  • Quality assurance for embankment compaction is one of very important procedures to guarantee high quality construction. However, only sand replacement method (KS F2312) and static plate load test (KS F2310) which are conventional and tiresome methods are used to evaluate degree of compaction at construction fields. Recently, new types of devices such as the geogauge and the light falling weight deflectometer (LFWD), the soil impact hammer (CASPFOL) and dynamic cone penetration test etc. which are able to substitute for the conventional methods are begun to use to evaluate soil stiffness. In this study, a laboratory model test was performed to evaluate correlations among test results obtained from the new devices and to assess the potential use of them. All test results have correlations with relative density and water content. Especially, the coefficients of correlation between $E_G$ from the geogauge and $K_{30'}$ from the soil impact hammer and between $E_G$ from the geogauge and $E_{LFWD}$ from LFWD are more than 0.7 but those between the results from DCP and others are less than those between $E_{G{\cdot}}$ and $K_{30'}$ and $E_G$ and $E_{LFWD}$.

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